1. Field of the Invention
The present invention relates to magneto-resistance effect type magnetic head devices and, more particularly, to a magneto-resistance effect type magnetic head device suitable for a rotating drum.
2. Description of the Related Art
A magneto-resistance effect type magnetic head (hereinafter referred to as "MR head") is configured using a magnetic layer having a magneto-resistance effect (hereinafter referred to as "MR film") and has a thin film type structure which allows the device to be more suitable for mass production and to be more compact as a whole. In addition, it can directly respond to a signal magnetic field independently of its speed relative to a magnetic recording medium to provide high reproduction output, which is advantageous in that high reproduction output can be obtained and in that multi-track configuration can be easily implemented. Therefore, this type of device has increasing demand in the application thereof to reproduction heads for fixed head type magnetic recording apparatuses.
A description will now be made with reference to FIGS. 11(A), 11(B), 12, 13, and 14 on examples of configurations of a yoke type single-channel MR head and a yoke type multi-channel MR head (hereinafter single-channel MR heads and multi-channel FIR heads are collectively referred to as MR heads).
FIGS. 11(A) and 11(B) show a single-channel MR head 13. FIG. 12 is a sectional view of a major part of a multi-channel MR head 14. FIG. 13 is a partial exploded view of the multi-channel FIR head 14 in FIG. 12. FIG. 14 is an overall exploded view of the multi-channel MR head 14 in FIG. 12. In FIGS. 11(A), 11(B), 12, 13, and 14, the multi-channel MR head 14 can be regarded as an MR head configured by integrating a plurality of single-channel MR heads 13 on the same substrate. Therefore, those MR heads will be described with parts serving like functions indicated by like reference numerals.
In FIGS. 11(A), 11(B), 12, 13, and 14, reference numeral 1 designates a non-magnetic substrate, and the non-magnetic substrate 1 is coated with a magnetic film layer made of a Fe-Si-Al type alloy which forms a lower yoke 2. The lower yoke 2 is coated with a silicon oxide film which constitutes a gap spacer layer 4 for forming a gap 3. Reference numeral 5 designates a bias conductor which is formed by a band-shaped copper material and is common to all channels. The bias conductor 5 is insulated by an insulation film 6 surrounding it which is constituted by a silicon oxide film. It serves as a path of a bias current for applying a bias magnetic field to an MR film 7 from a power supply connected between bias conductor terminals 5c and 5d.
The MR film 7 is coated with a pair of upper yokes 8a and 8b made of a pennalloy on both sides thereof, the upper yoke 8b being connected to the lower yoke 2.
One end of each of the upper yokes 8a and 8b rides on the bias conductor 5 and MR film 7 and constitutes a magnetic circuit as a core extending across those yokes.
A sense conductor 10 to be used as a signal line is provided on the MR film 7 and upper yokes 8a and 8b with an insulation film 9 constituted by a silicon oxide film or the like interposed therebetween, one end of the conductor 10 being connected to the upper yoke 8a. A non-magnetic film 11 made of Al.sub.2 O.sub.3 is provided on the sense conductor 10, and a non-magnetic protection plate 17 is provided on the non-magnetic film 11.
A surface 15 on which a magnetic recording medium is slid is formed so that the gap 3 faces a magnetic recording medium, e.g., a magnetic tape, by grinding the front faces of the non-magnetic substrate 1, lower yoke 2, gap spacer layer 4, upper yoke 8a, non-magnetic film 11, and non-magnetic protection plate 12.
A magnetic circuit is constituted by a loop formed by the lower yoke 2, magnetic gap 3, upper yokes 8a and 8b, MR film 7, and lower yoke 2.
Thus, a single-channel MR head 13 or multi-channel MR head 14 is provided.
In the single-channel MR head 13 or multi-channel MR head 14, when signal magnetic flux from the gap 3 which contacts a magnetic recording medium flows through the above-described magnetic circuit, the resistance of the MR film 7 in this magnetic circuit changes with an external magnetic field produced by this signal flux. Conventionally, a sense direct current to detect the change in the resistance of the MR film 7 flows through the sense conductor 10, and a direct current flows through the bias conductor 5 as a bias current to generate a predetermined bias magnetic field. With this bias current, the MR film 7 linearly operates to exhibit change in resistance which depends on the signal magnetic flux, the change in resistance being output as change in the voltage across the MR film 7.
It has been desired to use MR heads as described above which are advantageous in that they provide high reproduction output in rotating drum type magnetic recording apparatuses. However, in rotating drum type magnetic recording apparatuses which mostly employ signal transmission through a rotary transformer, it has been inevitable to employ a signal transmission system utilizing a rotating element such as a slip ring and brushes suitable for the transmission of a direct current for MR heads as described above which involves the transmission of a direct current to supply the bias current and sense current. This has resulted in a cost increase and has made it difficult to make such apparatuses more compact.
There is a possible method wherein an integrated circuit for converting an alternating current obtained from a rotary transformer into a stable direct current is incorporated in the rotary drum to supply the bias current. However, this method is too expensive to put it in practical use.
Since an MR head can provide high output even at a low medium speed, the application of an MR head to a rotary drum type recording apparatus provides an advantage in that the speed of the apparatus can be low relative to the tape. In this regard, in conventional rotating drum type magnetic recording apparatuses, the transfer speed of the recording signal must be increased in order to obtain higher image quality. Most digital video tape recorders employ transfer speed on the order of 10 to several tens Mbps.
In addition, it is desired that the difference in speed between the tape and head is reduced to reduce wear that occurs therebetween; the sound produced during the rotation of the drum is reduced; and the mechanical precision of the drum which has been required for high speed rotation is relaxed to achieve a cost reduction with the tracking accuracy between the tape and head maintained. Such demands are incompatible with the need for increasing the transfer speed as described above.
It is an object of the present invention to provide an MR head which provides the advantages of an MR head as described above, in which a rotary transformer can be used with facility, and which provides high reproduction output. In addition, it is an object of the invention to provide a multi-channel MR head which has been more difficult to provide as the track density increases in the case of an inductive type head.